Graphical rolled steel sheet flatness display and method of using same

ABSTRACT

A method for measuring and displaying the flatness of a rolled steel sheet is disclosed that includes the steps of measuring tension in the sheet at a plurality of locations on the surface of the sheet and determining a plurality of tension ranges into which the sensed tension level can fall. A color is associated with each of the tension ranges, and a representation of the sheet is produced that is made up of a plurality of regions, each region having a color corresponding to tension range into which the tension sensed at the corresponding location on the surface of the sheet falls. A device for carrying out this method is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/350,353now U.S. Pat. No. 6,948,347, filed Jan. 24, 2003, which is acontinuation in part of application Ser. No. 10/347,503 filed Jan. 21,2003 now abandoned, entitled Graphical Rolled Steel Sheet FlatnessDisplay and Method of Using Same” by inventors Thomas J. Russo, et al.,the disclosures of which are incorporated herein by reference and towhich priority is claimed under 35 U.S.C. §120.

REFERENCE TO COMPUTER PROGRAM LISTING APPENDIX

The computer program listing appendix contained in the file“FlatnessDisplayListing.txt” on compact disc 1 of 1, which has beenfiled with the United States Patent and Trademark Office in duplicate,is hereby incorporated by reference. The file was created on Dec. 10,2002, and is 17,363 bytes in size.

FIELD OF THE INVENTION

The present invention is directed toward a graphical flatness indicatorfor a sheet of rolled material and a method of using this device, and,more specifically, toward a device that receives signals indicative oftension levels in a rolled steel sheet and produces output signals thatgenerate, on a display, in real time, a color representation of asurface of the rolled steel sheet, wherein different colors on therepresentation correspond to different sensed tension levels in therolled steel sheet, and toward a method of using the device.

BACKGROUND OF THE INVENTION

Steel sheet may be processed by cold rolling in a rolling mill toincrease its strength. This is done by passing the sheet between a pairof rollers spaced by a distance less than the thickness of the sheet. Inpractice, owing to bending or expansion of the rollers, the pressureapplied to the sheet is not completely uniform in either the length orwidth direction. This lack of uniformity produces internal compressionand tensile stresses in the sheet that vary along its length and/oracross its width.

In general, a steel sheet that has a uniform tension distribution willlie flat on a horizontal table if it is unwound and set down with thetension removed. Steel sheet having a non-uniform tension distributiondoes not generally lie flat, but instead has wavy or buckled portionsthat correspond to the areas of the sheet rolled with the lowesttension. Thus, the flatness of a sheet may be determined by measuringits tension distribution. Examples of tension measuring devices thatmake use of this fact can be found, for example, in U.S. Pat. No.5,537,878 to Sendzimir and U.S. Pat. No. 3,499,306 to Pearson, thedisclosures of which are hereby incorporated by reference.

The data produced by such tension sensors may be analyzed by computer todetect tension distributions that are outside normal ranges. However,merely detecting whether tension levels are too high or too low does notgive complete information regarding the flatness of the sheet. Prior artdevices may allow a sheet to be generally characterized as eitheracceptable or unacceptable, but provide little useful information as tohow the tension varies across the length and width of the sheet. If moredetails concerning the tension distribution were available, decisionscould be made concerning which portions of the sheet might be acceptablefor some uses. Moreover, if information concerning the flatness of thesheet were available in real time, an operator might quickly determinewhat was causing an out-of-flatness condition and take the appropriatesteps to correct the problem.

It is therefore desirable to provide a method and apparatus forreceiving tension signals from a plurality of sensors measuring tensionin a rolled sheet, and providing an output that produces, on a display,in real time, a representation of the flatness of the sheet.

SUMMARY OF THE INVENTION

In a first aspect, the invention comprises a graphical flatness displayfor a rolled steel sheet that includes at least one sensor for measuringa property of a rolled steel sheet at a plurality of locations on thesheet and producing a property output signal corresponding to amagnitude of the sensed property at each of the plurality of locations.A processor is operatively connected to the sensor and receives thesensor property output signals. Property magnitude ranges and a colorcorresponding to each of the property magnitude ranges are stored in amemory connected to the processor, and a color display is operativelyconnected to the processor. The processor receives a property outputsignal, determines the property magnitude range indicated by the outputsignal, and plots a point in the color corresponding to the propertymagnitude range on the display. The plot is made at a point on thedisplay related to the location on the rolled steel sheet at which theproperty was sensed.

Another aspect of the invention comprises a method of indicating theflatness of a rolled steel sheet that involves measuring tension at aplurality of points across a first segment of the sheet and generatingan output signal related to the tension sensed at each of the pluralityof points. Then a representation of the first segment of the rolledsteel sheet is displayed that includes regions corresponding to each ofthe plurality of points. A color at each region is related to thetension measured at the corresponding one of the plurality of points onthe sheet.

Another aspect of the invention comprises a device for depicting theflatness of a rolled steel sheet in real time. The device includes aprocessor operatively connected to a sensing device that measurestension at a number of points on a rolled steel sheet and producestension output signals related to sensed tensions. Numeric values basedon the tension output signals are stored in a database, while colorscorresponding to ranges of the numeric value are stored in a memory. Theprocessor produces signals on a real-time basis to create a color imageof the rolled steel sheet on a display with regions on the displaycorresponding to points on the rolled steel sheet, wherein the colors ofthe regions on the display are related to the tension level sensed atthe corresponding points on the rolled steel sheet.

Another aspect of the invention is a device for monitoring theperformance of a steel rolling mill that includes a plurality of sensorspositioned to sense tension at selected points along the width of arolled steel sheet being processed in the rolling mill. Each of thesensors produces an output signal proportional to the sensed tension. Aprocessor is operatively connected to the tension sensors for receivingthe sensor output signals, while a memory is operatively connected tothe processor. The memory stores tension ranges and a colorcorresponding to each of the tension ranges. A color display isoperatively connected to the processor. The processor produces arepresentation of the surface of each sheet of rolled steel beingprocessed in the rolling mill on the display. The representationcomprises a plurality of regions corresponding to selected points on thesurface of the sheet with the color of each region corresponding to thetension range into which the sensed tension at the correspondingselected point falls. The representations of the surfaces of each sheetemerging from the rolling mill also includes a centerline, and thecenterlines of adjacent sheets of rolled steel are aligned.

Another aspect of the invention is a device for displaying tensionlevels in a steel sheet that includes a processor operatively connectedto a plurality of tension sensors for measuring tension at a pluralityof locations spaced across the width of the sheet and producing anoutput signal corresponding to the sensed tension. A memory isoperatively connected to the processor and stores tension ranges and acolor corresponding to each of the tension ranges. A color display isoperatively connected to the processor. The processor produces processoroutput signals for generating a color image on a color display, theimage comprising regions corresponding to the plurality of locations,the color of each of the regions corresponding to the range into whichthe sensed tension falls.

An additional aspect of the invention comprises a method of measuringthe flatness of a sheet of rolled steel that includes the steps ofmeasuring the tension at a plurality of measurement points on thesurface of a sheet of rolled steel, determining a plurality of tensionranges into which the sensed tension level can fall, associating a colorwith each of the determined tension ranges, and displaying arepresentation of the sheet of rolled steel. The representationcomprises a plurality of regions corresponding to the plurality ofmeasurement points and the color of each region is the color associatedwith the tension range into which the measured tension for eachmeasurement point corresponding to each display point falls.

Another aspect of the invention comprises a real time flatness displaythat includes a processor connectable to a sensing device for measuringflatness at a number of points on a rolled steel sheet and producing anoutput signal corresponding to sensed flatness. A memory is operativelyconnected to the processor and stores color information for each sensedflatness. The output signal produces on a display a two-dimensionalimage of the sheet of rolled steel comprising a plurality of regionseach corresponding to one of the plurality of points on the sheet ofrolled steel. The color of each region is related to the sensed flatnessat the corresponding point on the rolled steel sheet.

Still another aspect of the invention comprises a display having firstand second display fields where the first display field displays acolored representation of a planar surface of a rolled sheet of steelwith different colors on the colored representation representingdifferent tension levels in the at least one rolled sheet of steel. Thesecond display field comprises a colored representation of averagetension levels along a portion of the rolled steel sheet.

Another aspect of the invention comprises a method of indicating theflatness of a first rolled sheet of steel rs_(i) comprising thefollowing steps:

a) providing a first rolled sheet of steel rs_(i) having a plurality ofwidth segments w_(l) . . . w_(m) along a length of the first sheet ofrolled steel rs_(l);

b) providing a sensing device having a plurality of sensors d_(l) . . .d_(l);

c) measuring a tension at a number of points x_(l) . . . x_(n)acrosseach width segment W_(l) . . . W_(m) of the first sheet of steel rs_(l);

d) generating output signals having a value s_(l) . . . s_(n) related tothe tension sensed at each point x_(l) . . . X_(n) for each widthsegment w_(l) . . . w_(m);

e) for each width segment w_(l) . . . w_(m) storing the values s_(l) . .. s_(n) in a row r_(l) . . . r_(n)of a table t_(l) wherein each columnof the table comprises signals from one of the sensors d_(l) . . .d_(n);

f) associating a color with each of the output signals S_(l) . . . S_(n)based on the level of tension represented by the output signal; and

g) for each width w_(l) . . . w_(n) plotting points p_(l) . . . p_(n) ona display corresponding to points x_(l) . . . x_(f) on the width of thesteel rs_(l) wherein the color of each point p_(l) . . . p_(n) is basedon the level of tension represented by the output signals S_(l) . . .s_(n).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood after a reading of the detaileddescription of the invention provided below together with the followingdrawings.

FIG. 1 is a schematic side elevational view of a cold rolling mill and arolled steel sheet traveling over a tension sensor to a take-up roll.

FIG. 2 is a schematic representation of the system of the presentinvention including the tension sensor of FIG. 1, a central processorand a display.

FIG. 3 is a flow chart showing how data is gathered by the centralprocessor of the present system.

FIG. 4 is a flow chart showing how data from a database is used togenerate images on a display.

FIG. 5 is a detail view of region V of the display of FIG. 2.

FIG. 6 is a detail view of region VI of the display of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein the showings are for purposes ofillustrating a preferred embodiment of the invention only, and not forthe purpose of limiting same, FIG. 1 shows a cold rolling mill 10comprising a pair of rollers 12 supported on a frame 14, a tensionsensing device 16, a take-up roll 18 and a steel sheet 20. Steel sheet20 passes between the rollers 12 to strengthen the steel and is woundonto take-up roll 18 under tension. The tension in rolled steel sheet 20holds the rolled steel sheet 20 against tension sensing device 16,thereby allowing the internal tension at the portion of the rolled steelsheet 20 in contact with tension sensing device 16 to be measured. Itshould be noted that, while the invention herein is described inconnection with a cold rolled steel sheet, it could also be used tomeasure tension in a hot-rolled steel sheet or in a sheet of anothermaterial.

As best shown in FIG. 2, tension sensing device 16 comprises a pluralityof tension sensors 22 positioned along a rotatable drum 24 supported forrotation by supports 26. Such tension sensing devices are known in theart. The number and exact arrangement of sensors on the drum can bevaried as desired for a particular application. The preferred tensionsensing device 16 described herein has fifty-four tension sensors 22.

Each tension sensor 22 generates a signal indicative of the load againstthe sensor 22 when the sensor 22 engages sheet 20. The sensors 22 may,for example, include a piezoelectric element that generates a signalproportional to applied load. Because drum 24 rotates, each of thesensors 22 will be in contact with rolled steel sheet 20 for part of arotation only, and will thus periodically generate a signal each time itcomes into contact with rolled steel sheet 20. The sensors 22 arepreferably arranged in a spiral around the circumference of the drum 24,so that fewer than all sensors 22 are in contact with the rolled steelsheet 20 at any one time. Each sensor 22 will contact rolled steel sheet20 once for each rotation completed by drum 24.

The tension sensors 22 are operably connected to a local processor 28having a memory 30. Processor 26 is connected to a network 32, such as aLAN, WAN or the Internet, so that data concerning the sensed tension canbe remotely retrieved. Preferably, tension data is sent over network 32using UDP (user datagram protocol), a transmission protocol that offersa minimal transport service without the cumbersome error checking andother features of protocols like TCP.

A central processor 34 is also connected to network 32 and includes amemory 36. Various software runs on central processor 34 including datacollection software 38, a database 40, preferably a SQL Server™database, and shape display software 42. The operation of this softwarewill be described herein. Central processor 34 is operably connected toa display 44, either by line 46 shown in FIG. 2 or over network 32, andto a secondary database 48 and various users 50 over network 32.

The collection of tension data is well known from the prior art.However, prior art methods and devices were generally unable to extractuseful information from the data in a timely and informative way. Forexample, it would be useful to learn that one of the rollers in arolling mill had developed a defect as soon the effects of the defectbegan to become apparent in the sheet of material being rolled, insteadof hours later when the defect has degraded the quality of many rolls ofsteel sheet and potentially rendered them unusable.

The collection of data by data collection software 38 will be explainedwith reference to the flow chart of FIG. 3. References L1-L9 in theflowchart refer-to listings 1-9 in the code provided in the Appendix tothis application to indicate which listing is responsible for whichfunction. In a startup step 60, central processor 34 initializes localand global variables, and at step 62 initializes a communications socketto prepare to receive information over network 32. At step 64 aconnection to SQL Server database 40 is opened, and record sets areinitialized at step 66. At step 68, arrays are initialized totemporarily hold data received from tension sensing device 16. At step70, central processor 34 waits for data to arrive over network 32, andthis data is read at step 72. Socket data is copied from memory 36 intoa global variable at step 74, and the distance that strip 20 has movedfor each packet of data received from local processor 28 is calculatedat step 75. For example, if drum 24 includes fifty-four sensors 22distributed evenly about a six foot circumference, and local processor28 sends data at 250 ms intervals, the receipt of 27 tension readingsfrom local processor 28 would indicate that drum 24 had completed onehalf of a revolution and that strip 20 had moved three feet in thatquarter-second period. There is little if any slippage between strip 20and drum 24, and drum rotation thus provides a good indication of stripmovement. A determination is made at step 76 whether mill 10 is running.If mill 10 is not running, a debugging operation is carried out at step78. If mill 10 is running, data is entered into arrays in the database40 at step 80, the main database index value is incremented at step 82and the database main index is put into database arrays where needed ata step 84.

At step 86, a check is made to determine whether a new roll has beenstarted. Steel sheet 20 and other sheets processed by mill 10 are joinedtogether, such a by welding, to produce a continuous sheet with the endof one sheet pulling the beginning of a subsequent sheet through mill10. Sensors, which may be optical sensors 52 shown in FIG. 2, forexample, detect the presence of a weld and send a signal to centralprocessor 34 to indicate that a sheet end has been detected. If a newroll is not detected at step 86, additional data from local processor 28is placed into database 40 at a step 88. If a new sheet is detected atstep 86, new coil entry work is done at step 90 and product datainformation (PDI) data is loaded into database 40 and associated withtension data from the new sheet. This PDI data is stored in a secondarydatabase 48 and includes detailed information on the sheet being rolled.This information includes, for example, tolerance information for agiven sheet and the degree of flatness required for that sheet.

At step 92 a determination is made as to whether an event has occurredin the mill, and if an event has occurred, data concerning the event isstored in database 40 at step 94. If no event has occurred, adetermination is made at step 96 as to whether the sheet has moved agiven distance, such as six meters. This determination is made from thecalculation performed at step 75. If the sheet 20 has not moved thegiven distance, sheet data is averaged at step 98. If strip 20 has movedthe given distance, shape data is placed into a main shape display tablein step 100 before step 98 is carried out. From step 98, centralprocessor 40 returns to step 70 and waits for data to arrive overnetwork 32.

By following the above steps, database tables are created that includetension data from fifty-four points across the width of strip 20, thistension data being related to the tension in a short segment 102 ofstrip 20 equal to the circumference of drum 24 , and these tensionlevels are stored in a row of a database table. Each time drum 24rotates, fifty four additional data points are generated and stored inthe table. Each column in the table will correspond to the tensionlevels sensed by one of the sensors 22 on drum 24. Thus the first columnof the table will represent tension levels sensed at six foot intervalsalong a first longitudinal band 104 of strip 20 and the second column ofthe table will represent tension levels sensed at six-foot intervalsalong a second longitudinal band 106 of strip 20. The points at whichtension is sensed along each band will be slightly offset given thecircumferential offset of adjacent sensors 22 on drum 24.

The output signals from tension sensors 22 may be in any form, but arepreferably converted to “I-units,” a measure of flatness that usespositive and negative numbers to express the amount and direction offlatness deviations. I-units are explained in detail in ASTM standardA568/A568M which is hereby incorporated by reference.

Table 1 below is populated with arbitrary data to illustrate theoperation of the present invention. The values in the table are inI-units.

TABLE 1 TENSION LEVELS Sensor# 0 1 2 3 n-1 n Width 1 1.2 −4.5 −6.1 5.63.1 −0.6 Width 2 1.5 −5.0 −7.2 6.1 4.0 1.1 Width 3 1.1 −4.7 −6.8 5.9 4.11.0 Width 4 1.1 −4.5 −6.1 6.0 3.1 −0.2 Width 5 2.1 −3.8 −5.9 6.3 3.9−0.5 . . . Width m-1 1.3 −4.4 −6.2 6.4 3.2 −0.3 Width m 2.2 −3.7 −5.86.2 3.8 −0.4

I-unit range are defined as follow in central processor 34: −10 to −8,−7.99 to −6, −5.99 to −4, −3.99 to −2, −1.99 to −1, −0.99 to 0, 0 to0.99, 1-1.99, 2-3.99, 4-5.99, 6-7.99 and 8-10. A color is assigned toeach of these ranges. A preferred example of such a color assignmentappears below. While other color schemes could be used, the below colorassignment provides certain benefits that make it desirable.Specifically, under the below assignment, tension levels plotted ingreen colors are at acceptable levels. Orange and red are indicative oftension levels that require immediate attention, and blue regionsindicate problems that require less immediate attention. This use of redto identify serious conditions is consistent with most user's associateof red with a warning or alert.

TABLE 2 COLORS ASSIGNED TO TENSION LEVEL RANGES Tension level Color  −10 to −8 Dark Blue −7.99 to −6 Blue −5.99 to −4 Light Blue −3.99 to−2 Aqua −1.99 to −1 Green-Blue −0.99 to 0 Green     0 to 0.99 LightGreen     1 to 1.99 Yellow-Green     2 to 3.99 Yellow     4 to 5.99Orange     6 to 7.99 Red-Orange     8 to 10 Red

From this information, processor 34 creates another table wherein thetension levels are replaced with their corresponding colors. Table 3below is based on the above data:

COLORS ASSIGNED TO TENSION RANGES OF TABLE 1 Sensor # 0 1 2 3 n-1 nWidth 1 Yellow- Light Blue Orange Yellow Green Green Blue Width 2Yellow- Light Blue Red-Orange Orange Yellow- Green Blue Green Width 3Yellow- Light Blue Orange Orange Yellow- Green Blue Green Width 4Yellow- Light Blue Red-Orange Yellow Green Green Blue Width 5 YellowAqua Light Blue Red-Orange Yellow Green . . . Width m-1 Yellow- LightBlue Red-Orange Yellow Green Green Blue Width m Yellow Aqua Light BlueRed-Orange Yellow Green

This data is used by a graphing program, such as Olectra Chart byComponentOne, to create two separate graphical outputs shown in display44 in FIG. 2 and in more detail in FIGS. 5 and 6. The different stepsdescribed above may also be divided between software modules indifferent manners. For example, the color assignments may be made by thecharting software itself rather by another program running on centralprocessor 34.

The first graphical output 110 is displayed in a first region 112 ofdisplay 44 and shown in detail in FIG. 5. First graphical output 110comprises an image 114 of rolled steel sheet 20 plotted in color withdifferent colors representing different tension levels sensed by sensors22. Image 114 comprises a plurality of contiguous portions 116corresponding to the short segments 102 of rolled steel sheet 20measured each time drum 24 rotates. Each of these portions 116 isdivided into a number of regions 118, each corresponding to an area onrolled steel sheet 22 at which a given sensor has taken a measurement.Thus, even though each measurement taken by each of sensors 22 will be adifferent distance from an end of the rolled steel sheet, all will bewithin one short segment 102, and tension along the entire length of theshort segment 114 will be treated as constant. The length of shortsegments 114 can be decreased, for example, by using a drum having asmaller circumference. Based on the above data, the colors of theregions 118 in the first portion 116 of the image 114 , from the bottomto the top of the display, will be yellow-green, light blue, blue andorange. As data is added to Table 1, additional plots are made so thatimage 114 of strip 20 lengthens as more and more of the strip passesover tension measuring device 16.

The process can also be understood by treating rolled steel sheet 20 asa first sheet, rs_(l), of a plurality of similar steel sheets rs_(l) . .. rs_(n), each of which is divided in a lengthwise direction into aplurality of width segments w_(l) . . . w_(m). Each of sensors 22 onsensing device 26 is labeled, in the direction from left to right asseen in FIG. 2, d_(l) . . . d_(n). In the preferred embodiment, n=54,but n could be larger or smaller depending on the type of sensing deviceused. On a single revolution of drum 24 of sensing device 26, each ofthe sensors d_(l) . . . d_(n) measures tension at a point x_(l) . . .x_(n) across a single width segment, with sensors d_(l) . . . d_(n)corresponding to points d_(l) . . . d_(n) along the width segment. Eachtime drum 24 rotates, n measurements are taken at a group of pointsx_(l) . . . x_(n) on another one of the width segments w_(l) . . .w_(m). Each time the drum rotates, the n sensors generate n outputsignals having values s_(l) . . . s_(n) related to the tension sensed ateach point x_(l) . . . X_(n) on the width segment being sensed. For eachwidth segment, these values are stored in a row r_(l) . . . r_(m) of atable t_(l) so that all the values for a particular width segment arestored in a single row. Each column of the table therefore comprisessignals from one of the sensors d_(l) . . . d_(n). A color is associatedwith each of the output signals s_(l) . . . s_(n) based on the level oftension represented by the output signal. Finally, for each widthsegment w_(l) . . . w_(f), points p_(l) . . . p_(n) are plotted ondisplay 44 which points correspond to points x_(l) . . . X_(n) on thewidth of the steel rs_(l). The color of each point p_(l) . . . p_(n) isbased on the level of tension represented by the output signals s_(l) .. . s_(n) at the corresponding point x_(l) . . . x_(n).

This display provides an operator with the ability to visualize theflatness of the rolled steel sheet 20 in real time and to detectpatterns indicative of a problem with the rolling mill 10 or the steelitself much more readily than could be done by reviewing raw numericaldata from the sensors 22. In addition, first graphical output 110comprises additional images 120, 122, 124, 126, 128 and 130 ofpreviously rolled steel sheets (not shown) so that tension variationsfrom one sheet to the next can be compared. The images 120, 122, 124,126, 128 and 130 are aligned along their respective centerlines so thatportions of each sheet that were rolled by the same portions of rollers12 are aligned and can be compared. This allows defects in the surfaceof rollers 12 to be quickly detected by observing the similar tensionlevels they impart to aligned areas of successive rolled steel sheets20.

The data in Table 1 is also used to produce a second graphic output 132,namely a waterfall chart, shown in a second region 133 of display 44.This second region 132 is shown in greater detain in FIG. 6. To producethis second graphical output 132 , tension values in each of thefifty-four columns for a given rolled steel sheet are summed and dividedby the number of rows in the column. This provides an average value forthe tension level sensed by a given sensor over the length of sheet 20.

The width of the strip is shown along the x axis of the graph, and themagnitude of the average tension value for each longitudinal band 104,106 of the rolled steel sheet is plotted on the Y-axis, this pluralityof points forming a first slice 134 of the waterfall plot. Nineadditional slices 135-143 are also shown in FIG. 6; the front-most slicedisplayed represents data from the most recently rolled sheet.

The points are plotted in color based on the color correspondence ofTable 2. Thus the average of the numbers shown in column 0 of Table 1above is 1.5 which corresponds to the color yellow-green. The leftmostpoint on first slice 134 is thus plotted in yellow-green. Each point onfirst slice 134 thus has a color, even though it may be difficult todistinguish the colors of the fifty-four points along this line.However, the color data becomes more useful when a second slice 136 andsubsequent slices are plotted adjacent first slice 134 in the samemanner because corresponding points on each slice are connected by linesthat indicate the change between the point on one line and the point onthe other. Thus, for example, if a first point on the first slice 134 isyellow-green while the first point on the second slice 136 is yellow, aline will be plotted that shades gradually from yellow-green to yellowto show the transition.

First graphic output 110 and second graphic output 132 together providean operator with a detailed real-time data concerning the tension in agiven sheet and allow corrective action to be taken when tension levelsindicative of a problem are noted. Line 146, for example in FIG. 5 showsa low tension area in a rolled steel sheet that varies little from sheetto sheet. Observations at a greater level of detail may reveal that thisline 146 is actually a series of periodic points. This might suggestthat a surface defect on one of the rollers 12 is periodicallydecreasing tension in the sheets as they are rolled. Likewise, thesomewhat random distribution of colors at location 148 shows what appearto be normal operating conditions, and/or variations that are due moreto the structure of the rolled steel sheet 20 than to the effects of therollers 12. Likewise, stripe 150 in FIG. 5 shows an area of generallyconsistently high tension. This real time view also allows the effectsof changes to be seen in close to real time. For example, if, in orderto lower the tension represented by line 146 in FIG. 5 a certainadjustment is made to rolling mill 10, the effects of this adjustment onthe next sheet will be readily observable from the correspondingillustration on display 44.

FIG. 4 illustrates the steps followed in retrieving data from database40. At step 152, local and global variables are initialized. At step 154shape display software 42, which is preferably Olectra Chart shapedisplay software, connects to database 40. At steps 156 and 158, theshape display software is configured to create first graphic output 110and second graphic output 132. At step 160, PDI data for the sheet 20being processed in mill 10 is obtained from secondary database 48 anddisplayed on display 44 in step 162. At step 164, data representing60,000 feet of rolled steel sheet is obtained from database 40 andplotted in first region 112 at step 166. At step 168, a check is made todetermine whether a new sheet has entered the mill, by checking theoutput of optical sensor 52, for example. If a new sheet is notdetected, data representing the current 60,000 feet of sheet is updatedat step 164. This process continues, with new colored regionscorresponding to short segments 102 of sheet 20 being plotted in firstregion 112. Only data concerning the current 60,000 feet of sheet ismaintained; older data is removed from the tables of database 40 toprevent the size of the database 40 from slowing down the operation ofthe system. If a new sheet is detected, average tension values for eachband on each of the previous ten sheets are obtained from database 40 atstep 170 and used to form the waterfall plot in second region 133 atstep 172. PDI data for the new sheet is also obtained from secondarydatabase 48 and displayed on display 44 at step 174. The system thenreturns to step 164 and updates the display in first region 112.

It has been found that this use of color allows operators to quicklyspot trends and identify problems. While the numerical data generated bysuch as system could conceivably be processed to locate numberssuggestive of a problem, an experienced operator can often spot patternsmore quickly and more reliably than a machine relying upon statisticalanalyses. Moreover the information generated can be stored and laterassociated with the particular rolled steel sheet. If a particularrolled steel sheet is not sufficiently flat to satisfy the requirementsof a certain customer, for example, the saved date concerning itsflatness may allow persons to determine another use for which the rolledsteel sheet is suitable and/or to find portions of the rolled steelsheet that are acceptable for other uses. For example, if a problem iscorrected after 10 percent of the rolled steel sheet has been rolled,the 90 percent of the rolled steel sheet that is defect free may beusable for other purposes. By associating PDI data with each sheet, anoperator can also quickly determine whether the sheet is being producedto specification, as the degree of flatness variation that will beacceptable in a given sheet will vary.

The present invention has been described in terms of a preferredembodiment, it being understood that obvious modifications and additionsto this preferred embodiment will become apparent to those skilled inthe relevant art upon a review of this disclosure. It is intended thatall such obvious modifications and additions be covered by the presentinvention to the extent that they are included within the scope of theseveral claims appended hereto.

1. A graphical flatness display for a rolled steel sheet, comprising: atleast one sensor for measuring a property of a rolled steel sheet at aplurality of locations on the rolled steel sheet and producing aproperty output signal corresponding to a magnitude of the sensedproperty at each of the plurality of locations; a processor operativelyconnected to the at least one sensor for receiving said sensor propertyoutput signals, a memory operatively connected to said processor storingproperty magnitude ranges and a color corresponding to each of saidproperty magnitude ranges; and a color display operatively connected tosaid processor; wherein said processor receives a property outputsignal, determines the property magnitude range indicated by saidreceived property output signal, and plots a point in the colorcorresponding to the determined property magnitude range on the displayat a point on the display related to the location on the rolled steelsheet at which the property was sensed, wherein said processor producesan output for creating a first graphical image comprising a colorillustration of a flat surface of the sheet of rolled steel and a secondgraphical image comprising a waterfall plot of the average tensionsvalues.
 2. The display of claim 1 wherein said first and second graphicimages represent the flatness of multiple rolled steel sheets.
 3. Thedisplay of claim 2 wherein said first and second graphical images arebased on measurements taken by said at least one sensor.
 4. The displayof claim 1 wherein said illustration includes representations of shortsegments of said rolled steel sheet.
 5. The display of claim 4, whereinsaid at least one sensor comprises a plurality of sensors, and whereineach graphical image includes a plurality of regions, with each regioncorresponding to data from a respective one of said sensors.
 6. Thedisplay of claim 1, wherein: the first graphical image comprises colorillustrations of flat surfaces of first and second sheets of rolledsteel which have been rolled consecutively with one another, the colordisplay simultaneously displaying the color illustrations of the firstand second sheets to permit comparison therebetween; and the secondgraphical image comprises waterfall plots of the average tension valuesof the first and second sheets of rolled steel, the color displaysimultaneously displaying the waterfall plots of the first and secondsheets to permit comparison therebetween.
 7. A method of indicating theflatness of a first rolled steel sheet, comprising the steps of:measuring tension at a plurality of points across a first segment of atleast one rolled steel sheet; generating an output signal related to thetension sensed at each of the plurality of points; displaying first andsecond graphical representations of the first segment of the firstrolled steel sheet, each of the representations including a regioncorresponding to each of the plurality of points; and displaying at eachregion an associated color representative of the tension measured at thecorresponding one of the plurality of points, wherein the firstgraphical representation comprises a color illustration of a flatsurface of the sheet of rolled steel and the second graphicalrepresentation comprises a waterfall plot of average tensions values. 8.The method of claim 7, including the additional steps of: measuring thetension at a second plurality of points across a second segment of thefirst rolled steel sheet; generating an output signal related to thetension sensed at each of the second plurality of points; displaying arepresentation of the second segment of the first rolled steel sheetincluding a region corresponding to each of the second plurality ofpoints; and displaying at each region of the representation of thesecond segment an associated color representative of the tensionmeasured at the corresponding one of the second plurality of points. 9.The method of claim 7, including the additional steps of: a) measuringthe tension at a subsequent plurality of points across a subsequentsegment of the first rolled steel sheet; b) generating an output signalrelated to the tension sensed at the subsequent plurality of pointsacross the subsequent segment of the first rolled steel sheet; c)displaying a representation of the subsequent segment of the first sheetof rolled steel including regions corresponding to each of thesubsequent plurality of points; d) displaying at each region anassociated color representative of the tension measured at thecorresponding one of the subsequent plurality of points; and e)repeating steps a through d until an end of the sheet of steel isdetected.
 10. The method of claim 9, including the additional steps of:measuring the tension at a plurality of points across a first segment ofa second rolled steel sheet; generating an output signal related to thetension sensed at each of the plurality of points on the second rolledsteel sheet; and displaying a representation of the first segment of thesecond rolled steel sheet adjacent a representation of the subsequentsegment of the first rolled steel sheet, the representation of a firstportion of a second rolled steel sheet including a region correspondingto each of the plurality of points on the second rolled steel sheet; anddisplaying a color at each region related to the tension measured at thecorresponding one of the plurality of points on the second rolled steelsheet.
 11. The method of claim 7, including the additional step ofdisplaying a second graphical representation of the flatness of thesheet.
 12. The method of claim 7, wherein: the first graphicalrepresentation comprises color illustrations of flat surfaces of firstand second sheets of rolled steel which have been rolled consecutivelywith one another, the color illustrations of the first and second sheetsbeing displayed simultaneously to permit comparison therebetween; andthe second graphical representation comprises waterfall plots of theaverage tension values of the first and second sheets of rolled steel,the waterfall plots of the first and second sheets being displayedsimultaneously to permit comparison therebetween.
 13. A displaycomprising first and second display fields, comprising: said firstdisplay field displaying a colored representation of a planar surface ofa rolled sheet of steel wherein different colors on said coloredrepresentation represent different tension levels in said at least onerolled sheet of steel; and said second display field comprises a coloredrepresentation of average tension levels along a portion of the rolledsteel sheet, wherein said portion of the rolled steel sheet comprises aband extending from a first end of the rolled steel sheet to a secondend of the rolled steel sheet.
 14. The display of claim 13 wherein: saidfirst display comprises a first colored representation of the firstrolled sheet of steel and a second rolled sheet of steel; and the seconddisplay comprises a second colored representation of average tensionlevels along a first band of the first rolled steel sheet, a thirdcolored representation of average tension levels along a first band ofthe second rolled steel sheet, and colored lines connectingcorresponding points on said second colored representation and saidthird colored representation.
 15. The display of claim 14 wherein therepresentation of the average tension along a first portion of a firstrolled sheet of steel and a representation of the average tension alonga corresponding first portion of a second rolled sheet of steel areconnected by graphics showing the difference between the average tensionalong the first portion of the first sheet of rolled steel and theaverage tension along the first portion of the second sheet of rolledsteel.